Field discharge circuit breaker



May 4,- 1943- T. LINDSTROM FIELD DISCHARGE CIRCUIT BREAKER Filed Dec. 24, 1941 3 Sheets-Sheet l INVENTOR WITNESSES:

Patented May 4, 1943 FIELD DISCHARGE CIRCUIT BREAKER Ture Lindstrom, Edgewood, Pa.,

assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 24, 1941, Serial No. 424,301

Claims.

This invention relates to circuit breakers and more particularly to field discharge circuit breakers.

The shunt field windings of large separately excited generators are protected against excessive induced voltages by means of field discharge circuit breakers. An excessive voltage may be induced in the winding of a separately excited enerator when the generator is disconnected from its normal voltage supply. Such induced voltage may be of sufficient magnitude to rupture the insulation of the winding. For this reason, it is desirable to protect the Winding by providing the circuit breaker in such applications with a field discharge switch which closes when the breaker opens and connects a resistance across the shunt field winding for the purpose of discharging the induced voltage. A circuit breaker equipped with such a switch is usually referred to as a field discharge circuit breaker.

One object of the invention is the provision of a circuit breaker embodying an improved field discharge switch which is simple, more reliable and efficient in operation and which is more economical to manufacture and install than field discharge switches heretofore known in the art.

Another object of the invention is the provision of improved field discharge circuit breaker embodying a field discharge switch wherein the actuating mechanism for the switch 9 is mounted independently of said switch and is separable therefrom, the actuating mechanism being operable during an operation of the breaker to close and open the switch at the proper instants.

Another object of the invention is the provision of an improved field discharge circuit breaker embodying a field discharge switch wherein the actuating mechanism for the switch is mounted separately therefrom and which is provided with adjusting means for adjusting the airgap of the switch and for adjustably determining the time, during an operation of the breaker, at which the switch will close.

Another object of the invention is the provision of an improved field discharge circuit breaker embodying a field discharge switch biased to closed position and normally restrained in open position by an actuating mechanism which is mounted on a movable with the main breaker contacts and dish is operable during an operaticn of the breaker to release the switch at the proper time and permit the biasing means to close it.

Another object of the invention is the provision of an improved field discharge circuit breaker embodying a field discharge switch which is mounted separately from the circuit breaker mechanism, and an actuating mechanism mounted for movement with the breaker mechanism, said actuating mechanism having a part for cooperating with the switch to cause closing and opening thereof at the proper time during an operation of the breaker.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims, the invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Fig. 1 is an elevational sectional view taken substantially on line I-I, of Fig. 2 showing the contact structure of a circuit breaker embodying the principles of the invention.

Fig. 2 is a vertical sectional view taken substantially on line II--II of Fig. 1 showing the circuit breaker operating mechanism and the field discharge switch.

Fig. 3 is a fragmentary sectional view of the contact structure for the two poles of the breaker.

Fig. 4 is a fragmentary sectional view of the field discharge switch and the operating mechanism therefor in the position assumed when the breaker contacts are open and the field discharge switch is closed.

Fig. 5 is a fragmentary elevational view showing a modification of the field discharge switch and its operating mechanism in the open position.

Fig. 6 is a view of the mechanism shown in Fig. 5 but in the closed position of the field discharge switch.

Fig. '7 is a fragmentary front elevational view of the modification of the invention shown in Figs. 5 and 6.

Referring to Figs. 1 and 2 of the drawings, the field discharge circuit breaker comprises, generally, a base I! of insulating material, circuit breaker contact structure l3 (Figs. 2 and 3) for each of the two poles of the breaker, a field discharge switch indicated generally at i5, a

main frame I 6 having spaced sides I? rigidly connected at their inner ends by a cross member l9 and at their outer ends by a cross member 25, an arm extinguisher 2| for the contact means of each of the two poles, and a trip device indicated generally at 22.

spring 'to open the contacts.

The main frame It is mounted on the central portion of the base H and is secured thereto by means of bolts 23. The lower bolt 23 extends through an opening in the cross member 19 and serves to rigidly secure a member 25 to the cross member and to the base H. The member 26 is provided with an opening through which extends a shaft 29. The shaft 29 also extends through openings in the sides of the main frame it and pivotally supports a pair of parallel arms 3% disposed between the sides of the frame l5. At their free ends, the arms 3| are formed integral with a support member upon which is mounted a field discharge switch actuating device indicated generally at 32 (Fig. 2).

Rigidly clamped to the member 35 by means of a split clamp 1c and a screw H is a tie bar Bl extending transversely across the poles of the breaker. Identical contact arms 33 (Figs. 1 and 3) are rigidly secured to the bar 61 by means of split clamps l5 and screws H. The support member 35 and the contact arms 33 are insulated from the tie bar 61 by means of sheaths 69 of insulating material (Figs. 2 and 3).

The contact arms 33 are disposed on opposite sides of the main frame 16, and each arm 33 carries movable contact means illustrated in Fig. 3 which serve to open and close the main circuits of the breaker. The stationary contacts and the movable contact assemblages for the two poles are alike consequently only the contacts for one of the poles will be described.

Each contact arm 33 carries a main movable "contact member 4'! and a movable arcing contact ,member 55. The main contact member 61 is pivotally mounted on a pivot pin 49 supported in projections 51 (only one being shown) of the contact arm 33, and the movable arcing contact member 55 is pivoted on a pivot pin 51 supported 'in projections 59 (only one being shown) of the arm 33. The main movable contact member ll carries a contact 53, and a contact 55 is secured 'to thearcing contact member-55. The contacts 48 and 58 are adapted to cooperate respectively with fixed stationary contacts 35 and 3! secured on a conductor 41 which is in turn secured to the base II by means of bolts 43. The conductor l! extends upwardly and is bent at right angles, the'bent portion extending through an opening 'in the base II to form a terminal connector l5.

A spring 53 (Fig. 3) compressed between a seat on the contact arm 33 and a spring seat on the main contact member 41 provides contact pressure for the main contacts 35-48 when the contact arm is in the closed position. Contact pressure for the arcing contacts 31-59 is provided by a spring 63 surrounding a rod 61 which is pivotally connected to the arcing contact member 55 and which is slidable through an opening in a spring seat on the contact arm. 33. The

spring .63 is compressed between a washer 65 seated on a shoulder on the rod BI and the spring seat on the contact arm 33. The rod 6 I has a nut '15 on the outer end thereof which cooperates with the contact arm 33 to limit counterclockwise rotation of the arcing contact member 55 about its pivot when the contact arm 33 is moved Counterclockwise movement of the main contact member 61 (Fig. 3) is limited by a projection 13 thereon striking the body of the contact arm 33. The adjustment of the nut F5 on the rod BI is such that the arcing contacts 3l--50 open after the main contacts 35-48 have opened during an opening operation I of the breaker.

When the contact arms 33 are operated to open the contacts, the arcs across the arcing contacts resulting from the rupture of the current are drawn into arc-extinguishers 2i (Figs. 1 and 2) where they are cooled and quickly extinguished. Any suitable arc extinguisher may be employed, those illustrated comprising, generally, stacks of slotted plates of magnetic material disposed a-djacent the paths of travel of each of the arcing contact members 55. The plates serve to draw the arcs toward the apices of the slots where they are broken up into a plurality of short arcs which are quickly cooled and extinguished.

The movable arcing contact member 55 is connected by a flexible shunt conductor 'I'i (Fig. 3) to the main contact member 41 which in turn connected by means of a flexible shunt conductor 79 to a corresponding connector 2? (Fig. 1). The connectors 21 for the two poles are bolted to the base H with spacers (not shown) between the base and each of the connectors. To each of the connectors 21 for the two poles is secured by means of bolts 14, the upper end of a conductor (Figs. 1 and 2) which extends downwardly from the connectors 21' The conductors 8| are bent at right angles and the horizontally disposed portions thereof extend between the legs of cl-shaped magnet cores I6! (Fig. 2) forming part of the trip device 22. The conductors extend through openings in the base I! and form terminal connections 83 (only one being shown) which, together with the terminal connectors 45, serve to connect the poles of the breaker in electrical circuits,

The electrical circuits for the two poles of the breaker are essentially the same, therefore, only the circuit for one of the poles will be traced. This circuit extends from the terminal connector 45 (Fig. 3) through the conductor 4!, the main contacts 35 l8, the main contact member 41, the flexible shunt conductor 79, the connector El (Fig. 1), the conductor 3! to the terminal connector 83 (Fig. 2) The circuit for the arcing contacts 31-50 (Fig. 3) extends from the terminal connector A5, through the conductor 4|, the arcing contacts 3'l55, the arcing contact member 55, the flexible shunt conductor 71, the main contact member 41 and through the previously described circuit to the terminal connector 83.

The support member 35 (Fig. 2) for the-field discharge switch mechanism and the contact arms 33 are biased in a clockwise or opening direction by means of a pair of springs 85 (Figs. 1 and 2). These springs are tensioned between the support member 30 and a fixed pivot 87 supported in the main frame Hi. In the closed position of the main circuit breaker, the support member 39 and consequently the main contact arms 33 are releasably restrained in closed contact position in which the main contacts 3548 and the arcing contacts 31-455 (Fig. 3) are closed and the field discharge switch I5 is open. The movable contact assemblage is releasably restrained in the closed position by means of a toggle and linkage mechanism which is collapisble to cause opening of the main circuit breaker contacts and closure of the field discharge switch. The toggle and linkage forms a part of the common operating mechanism.

Thi collapsible linkage includes a lever 89 (Fig. 2) pivotally mounted on a fixed pivot 9| supported on the main frame 16. The lever 89 comprises a pair of levers rigidly connected by an -=knee pivot-pin 91.

more fully described later. link I03 each'comprise a pair .of members rigidly -09 in the overcenter positio-n,.as

the lever I05.

"integral cross bar III, and is operativelyconnected tothe support arms -3 I of the field disoperating toggle comprising toggle-links 93 and 95. The toggle link 93'hasone end pivoted on a pin IOI supported-on the lever '89, and the link "95 ispivoted-on a'pivot'pin -9'9on the arms 3|. Thelinks 93 and 95 are pivotally connected by a The'toggle link 95 comprises a pair of links rigidly connected by means of an integral cross member II 5.

The free end of the lever 59 is connected by 'meansof a link I03 to-onearm of a lever I05 pivotedon the fixed pivot 81. The other arm of the lever "I05 is pivotally connected to a toggle link I01 of a tripping togglecomprising the link It! :and a toggle link I09. The link.I09 is pivoted on a fixed pivot II3 supported on the frame It and comprises a pair of links joined near the pivot I I3 by a yoke I23 provided with projections I25 and I2I. The toggle link In! comprises a pair of links connected by a yoke! I9 having a bent portion to which is secured an extension IZI of insulating material. The toggle links I01 and I09 are pivotally connected by a knee pivot pin III. The

purpose of the extension I 2! is to cooperate with a partconnected .toiamanually operable handle I4! to manually trip the breaker in a manner to be Thelever I 05 and the connected by yokes substantially as illustrated. The linkage, just described serves to releasably hold the contact assemblage including the movable contacts for the two poles of the breaker in closed contact position. In the closed position. the main operating .toggle 93-95 is overcenter above a line through the center of the'pins 99-I I and a secondtoggle, one link of which comprises the overcen'ter links 9-395 and the other link of which comprises the lever 89, is overcenter above a line through the center of the pins 99 and 9!.

The overcenter movement of the main operating toggle 9395 is limited by the'projecting end of 'the link 93 engaging the cross member I I of the link 95.

With'the main operating toggle 93-95 and-the toggle comprising the links 9395 and the lever shown. .in.Fig. 2, the springs '85 bias the lever'89 in a clockwise direction. Movement of the lever 89, however, is normally prevented by the tripping toggle 'I0IIII9 whichis overcenter to the left of a line through thecenter of the fixed pivot I I3 and the :point of connection of the toggle link III! with The toggle .I0!I09 biased to its overcenter position by a spring I28 tensioned between the yoke 'I I9 and the fixed pivot H3. The overcenter position of the tripping toggle I0'I-I09 is adjustably determined by the projection I25 of the yoke [23 engaging an adjusting 'screw I29 in the cross member 25 of the frame. The tripping toggle I0'I'-I09 in its overcenter position, acting through the lever I05 and the link I03, prevents clockwise movement of the "cause its collapse to eifect opening of the breaker contacts by means of the trip device 22 (Fig. 2).

The trip device is operable in response to overload currents in the circuits of th breaker to 9 actuate a trip rod I35 andcause collapse of the tripping toggle I0II 09. The trip rod I35 is slidenergized from a suitable source and in a manner well known in the art, to operate the trip rod and trip the breaker from a remote point.

When operated either by the shunt coil or by the trip device 22, the trip rod I35 is thrust upwardly and strikes the projection I2! of the yoke I23 and rocks the toggle link I09 clockwise about the fixed pivot II3. This movement of the link I09 causes collapse of the tripping toggle Iii'II 09 permitting clockwise movement of the lever 89 which permits the springs to rock the movable contact assemblage clockwise to open the contacts. Movement of the contact assemblage to .open position effectsclosing of the field discharge switch I3 as will be fully described later.

The main operating toggle 93--95 does not immediately collapse but the force of the springs 85 appliedthrough the arms 3I and the main operating toggle causes collapse of the toggle comprising the links-9395 and the lever 89 which results in clockwise-movement of the lever 89.

This movement is transmitted through the link I93 and the lever I05 to complete the collapse of the tripping toggle I0II09.

The clockwise or opening movement of the support member 30 is arrested by projections (not 9! of the toggle has passed overcenter below the line 99-IOI the weight of the parts act to completethe collapse of the toggle 93--95 and causes the linkage 89, I03, I05 and the tripping toggle I0'I-I 09 to'be automatically reset to their normal position. The main operating toggle 93--95 remains in collapsed condition until the contacts are reclosed.

The contacts are closed manually by operation of the previously mentioned handle MI. The handle is rotatably mounted in a bracket I43 of insulating material secured to the outer end of the main frame I8. Operatively connected to the mechanism (not shown) operated by the handle is a link I5I. The lower end of the link I5! is recessed and straddles a pulley-shaped roller I53 rotatably mounted on a cross member l0! rigidly connecting the outer ends of a pair of spaced contact closing levers I45. Theselevers are disposed on the outside of the frame I0 and are pivctally supported on the ends of the fixed pivot SI which project beyond the sides of the frame It. The inner ends of the lever I45 are rigidly connected by a cross member I 49. Spaced projections I52 extending from the center portion of cross member I49 support a pivot pin I51 upon wh ch is rotatably mounted a roller I55.

The contacts are closed manually by clockwise rotation of the handle MI. This movement of the handle, through connections (not shown.) thrusts the link I5! downwardly and due to its engagement withthe roller I 53, rotates the closing lever I45 in a clockwise direction. During this movement of the lever I45, the roller I55 tripping toggle 'I0II.)9 has been restored to its overcenter position, rotation of the lever 89 is prevented and consequently the force applied by the roller I55 to straighten the toggle 93-95 rotatesthe arms 3! counterclockwise to close the contacts for the two poles and to tension the springs 85. Counterclockwise movement of the arms BI and of the support member as effects opening of the field discharge switch I5. The clockwise movement of the closing lever I45 moves the toggle 99-95 overcenter above the line 99I iii so that the contacts are held in the closed position until the breaker is again tripped.

Upon release of the handle MI following a contact closing operation, 'a spring I59 (Fig. 2) tensicned between the closing lever I45 and a point on the frame It restores the lever M in a counterclockwise direction. This movement of the lever I and the roller I53 thrusts the link I upwardly to restore the handle MI to its neutral position.

The closing lever I45 may be operated to autoable source. When energized, the motor is adapted, through a suitable driving connection, to rotat-e a crank disc I39. This disc carries an antifriction roller I3I which engages a cam face I32 on an arm IS S secured to one side of the closing lever and rotates the arm and the closing lever M5 clockwise to efiect closing of the contacts in the previously described manner. As soon as the roller ISI passes out of engagement with the arm I3 1, the spring I59 acts to restore the lever I45 to its normal position. The motor I39 is deenergized by a suitable limit switch (not shown).

The circuit breaker may be tripped manually by rotation of the handle I 4| through a small angle in a counterclockwise direction from its neutral position. When the handle is rotated in tripping direction, a projection (not shown) on the link I5I engages the extension I2I on the yoke I Is of the toggle link I61 and rocks the link counterclockwise about its point of connection with the lever I95. This moves the tripping toggle Iii1 IIi9 overcenter in a direction to cause its collapse and effects opening of the contacts in the previously described manner.

As previously stated, the trip rod I35 is operated to efiect tripping of the breaker by means of a current responsive trip device 22. There is a trip device 22 provided for each of the two poles of the breaker but since the trip devices are alike only one will be described.

The trip device includes the U-shaped magnet core I5! and a frame comprising substantially parallel side members I53 rigidly connected at their outer ends by a yoke I65. The members I53 are provided with mounting feet I51, and bolts 3% (only one being shown Fig. 2) extend through openings in the feet I61 and in the magnet core ISI and in the base I I to rigidly secure the core and frame to the base. A trip lever I13 is pivotally supported on a pivot I15 mounted in the frame I63. The trip lever I13 comprises a pair of spaced levers having an armature I19 secured to one end and being rigidly connected by a yoke $71 at the other end. The trip lever I13 is biased against operation by the magnet MEI by means of pair of springs I9I (Fig. 2, only one being shown) having one end secured to the yoke I11 and the other end attached to a vertically movable plate I93. The plate I93 cooperates with an adjusting screw I95 which is provided with a knurled head I91 bearing against the bottom side of a formed projection I99 of the yoke I65. Rotation of the screw I95 moves the plate I93 and thereby adjusts the tension of the spring |9l to vary the tripping characteristic of the breaker. A scale plate 2 93, supported on spaced projections 29I of the yoke I65, bears indicia indicating the adjustment of the spring I9I or the tripping point of the breaker. An adjustable stop screw 205 provided with a lock nut 291 determines the open air gap of the magnet.

A trip bar I81 is rotatably supported in a bracket I89 secured to the casing I38 for the shunt coil. The trip bar extends transversely across the poles of the breaker and is provided with an arm I85 for each of the poles, and a center arm I85 on the trip bar is in alignment with the lower end of the trip rod I35. An adjusting screw I3I is mounted in each of the yokes I11 in alignment with the corresponding arm I85.

Normal rated current flowing through the circuit of the breaker, including the conductor 8|, causes slight energization of the magnet I5l but not sufiicient to overcome the tension of the springs I9I. Upon the occurrence of an overload current above a predetermined value in the circuit of either of the poles, the flow of current through the conductor SI causes energization of the magnet sufiicient to overcome the springs I9I and attract the armature I19 rocking the trip lever I13 counterclockwise. At this movement of the trip lever I13, the screw I8I rotates the arm I85 and the trip bar I81 in a clockwise directicn and thrusts the trip rod I35 upwardly to trip the breaker in the previously described manner.

The construction of the circuit breaker as thus far described with the exception of the field discharge switch and the trip device 22 is essentially the same as that fully disclosed in the copending application of John W. May and Ture Lindstrom, Serial No. 391,625, filed May 3, 1941, and assigned to the assignee of this invention.

In the illustrative embodiment of the invention, the field discharge switch I5 (Figs. 1, 2 and 4) is located in the position which would ordinarily be occupied by the contact assemblage of the center pole of a three pole breaker. The field discharge switch I5 comprises a switch member 299 pivotally supported on a pivot pin 2 I I mounted in the two arms of a bifurcated member 2I3 of conducting material. The member 2I3 is secured to the base I l by means of a shouldered bolt H5 integral with the member 2 I 3, and a nut 2 I 1. Similarly secured to the base I! by a shouldered bolt 2I9 and a nut ZZI is a contact member 223 with which the free end of the switch member 299 is adapted to cooperate to close a circuit for connecting the shunt winding of a generator-(not shown) to a resistance (not shown). The bolts 2I5 and 2I9 project beyond the nuts 2E1 and HI and form terminal connectors for connecting the field discharge switch to the circuit.

The switch member 299 is biased in a counterclockwise (Fig. 2) or closing direction by means of a spring 225 having one end hooked through an opening near the free end of the switch mem-' her and the other end anchored to a pin 221 supported by a bracket 229 integral with the members 2I3 and which is secured to the base II by the shouldered bolt 2| 5 and member 2I3. The pin 221 projects into the base II to prevent rotation of the bracket 229 and the member 2I3.

The switch member 2&9 is provided with a downwardly extending tail 23I having an arcuate surface 233 with which the field discharge switch operating mechanism 32 cooperates to restrain the switchvmember 209 in open position when the main circuit breaker is in the closed position. The operating mechanism 32 comprises a roller 235 rotatably mounted. on a pin 231 supported in an arm 239. The arm 239 is pivotally supported on a pivot pin 24! mounted in a pair of ears243 formed on the upper end of a bracket 245 which is rigidly secured to the support member- 30. The arm 239comprises a pair of identical arms (Fig. 1) spaced apart by means of the roller 235 and a spacer 241 mounted on a pin 249 supported on the arms 239. The arms 239 are provided with shouldered projections 25! which ade adapted to engage the body of the bracket 245 to limit clockwise travel of the arms. The arm 239'is biased in a clockwise direction by means of a spring 253 coiled around the pivot pin 241 and having one end bearing against the-member 30 and the other end bearing against the spacer 241. A headed bolt 251 threaded into the support member 39 passes through an opening in the bracket 245 and is adjustably secured thereto bymeans of a lock nut 259. The head 255 of the bolt engages the roller 235 when the main breaker is in cosed position to restrain the switch memher in open position.

When the main circuit breaker is operated to the open position, as previously described, and the arms 3! and the member 30 move clockwise, the-spring 225 rotates the switchmember 239 in a counterclockwise direction maintaining the tail 23! in contact with the roller 235 and the roller in contact with the head 255 of the bolt 25'! untilthe movement of the switch member-2fi9 is arrested by engagement of its free end with the contact member 223. Theclosing of the switch i5 is arranged to occur just an instant before the arcing contacts31 and 59 disengage during opening of the breaker. Upon continuedm'ove ment of the main contact assemblage in opening direction, the spring 253 expands and rotates the arm 239 in a clockwise direction until the move.- ment thereof is arrested by engagement ofthe projections 25| with the bracket 245; In Fig. 4, the parts are shown with the main breaker "contact assemblage in the open position and th field discharge switch l5in the closed position.

In this position, 'it'may be observed that the center line 231-24I of the arm 239 is above a line-tangent to the radius 29-24l. When the arms-3| and the support member 30 are rotated in-a counterclockwise or'closing direction in the previously described manner, the roller 235 will engage thearcuate surface 233 just prior to engagement of the breaker contacts and start the switch member in a clockwise direction toward open-position. At thetime of engagement of the roller -235 with the tail 23l of the switch member 209, the angle subtended by a line drawn tangent to the surface 233 at the point of contact.

of the roller 235, and a line drawn through said point of contact and center of the pivot 24! is greater than 90. Continued movement of the member 30 toward closed position of the main circuit breaker rotates the switch member 209 in a clockwise or opening direction, thus reducing this angle and separating the contacts 209223. As soon. as the angle becomes less than 90, the force of the spring 225 overcomes the relatively light force of the spring 253 and causes collapse of the arm 239. During the collapsing movement of the arm 239, the roller 235 travels downwardly along the surface 233 until it strikes the head 255 of the bolt 251. The parts are shown in Fig. 2 in the fully closed position of the main breaker contacts.

Referring to Fig. 2, it can be seen that the bolt 251 and the roller 235 determine the amount of separation of the contacts 209 and 223 when the circuit breaker contacts are in fully closed position and also determinesthe time of engagement of said contacts during the opening movement of the main breaker contacts. Adjustment of the illustrated in the position ordinarily occupied bythe-center pole of a three polebreaker, it is to be understood that the switch [5 may be mounted in place of either of the outer poles without affecting the operation of the switch or of the main circuit breaker. The field discharge switch.

has been illustrated for convenience in connection with a two pole circuit breaker. It is not desired to limit the use of the switch to'a two pole circuit breaker as it can be as readily applied to any circuit breakerof the general type illustrated having one or more poles.

According to the modified form of the invention illustrated in Figs. 5, 6 and 7, the field, discharge switch may be mounted in the space between-any two poles ofthe breaker without reducing the number of effective poles in the maincircuit breaker and without affecting the operation of thebreaker.

The-modified form of the invention shown in Figs. 5 to 7 is illustrated in connection with the circuit breaker mechanism shown in Figs. 1, 2 and 3 and like parts have been given the same reference characters. The circuit breaker 'inthis case is of the three pole type, only two poles beingshown (Fig. 7). The main contact structure is identical with that shown in Fig. 3; and the'operating mechanism is the same as'that illustrated in Fig. 2 for which reason a description of these mechanisms is not repeated in conjunction with the following description of the modification of the invention.

Referring to Fig. 5 of the'drawings, the modification of the invention comprises a-field dischargeswitch 26! mount'edon the base ll of the circuit breaker, for-the switch mounted on the tie bar 61 of the circuit breaker. The switch 26| bifurcated support member 255 for pivotally sup porting a switch member 261. is secured" to the base H by means of a bolt 26! and a nut 21!. The bifurcated end of the'mem her 255 pivotally supports the switch member: 251 on a pivot pin 213, and a contact support member 2?5 disposed adjacent th'e'free end of theswitcli member 261 is secured to the :base I by means of a bolt 211 andja nut 219. The contact support member 215 is bifurcated and a cylindrical contact 281' is supported on a stud'283 secured in the forks of the member 215. The free end of the switch member 261 is disposed between the forksof the contact support member 215 and has a beveled portion'which' is adapted; upon opening of the'oontacts of the breaker, to engage the cylindrical contact 28! to close thecircuit for connecting the shunt field and an actuatingmeans 263- includes a The member 265 winding of a generator to a field discharge resistance.

The switch member 26'! is actuated to closed position by means of a coil spring 235 but is restrained in open position by the operating mechanism 233 when the main breaker is in closed position. The spring 285 surrounds a pilot rod 23'! and is compressed between a yoke 289 secured to one'end of the rod and a spring seat in the base H. The arms of the yoke 239 embrace the switch member 231 and are pivotally connected thereto by means of a pivot pin 29!. The left hand end of the rod 281 (Fig. is slidablein an opening in the base II.

The actuating mechanism 233 for the field discharge switch member 231 includes a roller 293 rotatably mounted on a pin 295 mounted on the free ends of a pair of spaced arms 29?. The arms 29'! are pivotally mounted on a pin 299 supported in ears 39! formed inwardly from a bracket 393 which is mounted on the tie bar 61 for movement therewith. The bracket 393 is rigidly secured to the tie bar 61 by means of screws 399 which pass through openings in the bracket and are threaded into a plate 39? disposed on the opposite side of the tie bar from the bracket 393. A rectangular sheath 69 of insulating material disposed between the tie bar 37 and bracket 393, plate 391 and screws 395 insulates the operating mechanism 263 from the tie bar and from the poles of the breaker.

The arm 29'! is biased in a counterclockwise direction by means of a coil spring 393 surrounding the pivot pin 299 and having one end bearing against the bracket 393 and the other end bearing against a spacer 3H rigidly connecting the arms 291. When the main contact assemblage is in the closed position (Fig. 5) an adjustable stop bolt 313 secured in the upper end of the bracket 333 by means of a lock nut 3E5, cooperates with the roller 293 to hold the switch member 291 in its open position against the biasing force of the spring 285.

. When the main circuit breaker is operated to open position, the tie bar 91 and the actuating,

mechanism 263 are moved clockwise from the Fig. 5 position to the Fig. 6 position, moving the contact assemblages for the several poles of the breaker to open circuit position. During this movement, the spring 285 expands causing the switch member 261 to maintain contact with the roller 293 and to maintain the roller in contact with the head of the stop bolt 3l3 until the beveled portion of the switch member engages the cylindrical contact 28! and arrests the movement of the switch member. This occurs just before the arcing contacts 31-59 of the circuit breaker separate. As the actuating mechanism continues its clockwise travel, the spring 399 rocks the arm 2 91 counterclockwise about the pivot 299 until the counterclockwise movement of the arm 29'! is arrested by the spacer 3| l striking the ears 30l of the bracket 393. The parts are shown in Fig. 6

with the main breaker contact assemblage in the fully open position and with the field discharge switch in closed position.

When the circuit breaker contacts are closed, in the previously described manner, the tie bar 6'! together with the actuating mechanism 263 is moved counterclockwise from the Fig. 6 position to the Fig. 5 position. Just before the arcing contacts touch, the roller 293 engages the switch member 231 and rocks it counterclockwise against the tension of the spring 295 in the opening direction. At the time of engagement of the roller with the switch member, thearm 291 is overcenter below a line drawn through the centeroi the pivot 299 and perpendicular to the right hand edge of the switch member 261. Continued movement of the actuating mechanism, therefore, causes the roller 293 to engage beveled corners iii? of angular portions 3I9 integral with forks of the support member 265. This cams the arm' 291 clockwise about the pivot 299. As soon as the arm moves overcenter above the line through 299 perpendicular to the edge of 261, the spring 283 overcomes the force of the relatively weaker spring 339 and rocks the arm 29'! sharply clockwise until it strikes the head of the adjusting screw 313.

By adjusting the screw 3l3 relatively to the bracket 333, the open air gap of the field discharge switch may be varied and the time of closing the field discharge switch in relation to ,the opening movement of the circuit breaker contacts may be adjusted.

Having described the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the structural details disclosed without departing from some of the essential features of the invention. It is, therefore, intended that the invention as set forth in the following claims be interpreted as broadly as the prior art permits.

I claim as my invention:

1. A circuit breaker comprising relatively movable contacts, a switch member movable to an open and to a closed position to open and close said contacts, operating mechanism for moving the switch member to open and to closed position, a field discharge switch including a stationary contact, a pivoted switch arm biased to a closed position, means for pivotally supporting said switch arm independently of the breaker operating mechanism, and means including a roller mounted on a part movable with the switch member for cooperating with the switch arm during operation of the breaker to cause closing and opening of the field discharge switch.

2. A circuit breaker comprising relatively movable contacts, a switch member movable to an open and to a closed position to open and close said contacts, operating mechanism for moving said switch member to open and to closed position, a field discharge switch including a stationary contact, a switch arm mounted on a fixed pivot independently of the switch member, means biasing the switch arm to closed position, and actuating means movable with the switch member for cooperating with the switch arm to permit said biasing means to close the field discharge switch when the circuit breaker switch member is moved to open position and to actuate said field discharge switch to open position when the circuit breaker switch member is moved to closed position.

3. A circuit breaker comprising relatively mov-- able contacts, a switch member movable to an open andto a closed position to open and close said contacts, operating mechanism for moving. said switch member to open and to closed position, a field discharge switch including a stationary contact, a switch arm pivotally mounted on a fixed pivot, and actuating meansfor the field discharge switch comprising a member piv otally mounted on the switch member and separable from said switch arm, said member being operable when the switch member is moved'to closed position to. actuate the switch arm to open position and being operable when the switch member is moved to open position to cause closing of the switch arm.

4. A circuit breaker comprising a switch member movable to an open and to a closed position for opening and closing t circuit, operating mechanism for moving sa Hitch member to open and closed position, a field discharge switch comprising relatively movable contacts, and actuating means for said contacts comprising a member mounted on the switch member and mcvable relatively thereto, said member being biased to one position to effect opening of said contacts during closing of thecircuit breaker and movable to another position to restrain said contacts in open position when the switch member is in closed position.

'5. A circuit breaker comprising a switch member movable to an open and to a closed position for opening and closing the circuit, operating mechanism for said switch member, a field discharge switch comprising a stationary contact and a movable contact biased in closing direction, actuating mechanism for said field discharge switch comprising a member pivotally mounted on said switch member-and biased to one position to eiiect opening of the contacts at a predetermined time during the movement of the switch member to closed position, said pivoted member being movable to another position .to restrain the contacts in open position when the switch member is moved to closed position.

6. A circuit breaker comprising a switch member movable to an open and to a closed position, operating mechanism for said switch member, a field discharge switch comprising a stationary contact and a pivoted switch arm cooperating therewith to close open said switch, actuating mechanism for said field discharge switch com rising an arm pivotally supported on the switch member, said arm being biased to an operating position and movable to a holding position, and means on said arm engageable with the switch arm at a predetermined time during movement of the switch member to closed position to effect opening of said field discharge switch and to cause movement of said arm to holding position.

7. A circuit breaker comprising relatively movable contacts, a switch member movable to an open and to a closed position to open and close said contacts, operating mechanism for moving said switch member to open and closed position, a field discharge switch comprising a stationary contact and a movable switch arm, a support member for pivotally supporting said switch arm, an actuating member for said switch arm pivotally mounted on a part movable with the switch member, said actuating member being biased to an operating position and operable during closing movement of said switch member to engage and actuate the switch arm to an open position, and means on the support member engageable by the actuating member to move said member to another position in which it restrains the switch arm in open position when the breaker is in closed position.

8. A circuit breaker comprising relatively movable contacts, a switch member movable to an open and to a closed position, operating mechanism for moving the switch member to open and to closed position to open and close the contacts, a field discharge switch comprising a stationary contact and a movable switch arm, a support member for pivotally supporting said switch arm,

actuating means for said switch arm comprising an arm mounted on the switch member and movable relatively thereto, means biasing the actuating arm to operative position, a roller on said actuating arm engageable with the switch arm when the switch member is moved to closed position to move the switch arm to open position, said actuating arm being moved to a restraining position by engagement with said support member, and means on the switch member engageable with said roller to restrain the switch arm in open position when the switch member is in closed position,

9, A circuit breaker comprising a switch member movable to open and closed positions, operating mechanism for moving said switch member to open and to closed position, a field discharge switch comprising a stationary contact and a cooperating switch arm, a support member for pivotally supporting said switch arm, an actuating arm for said switch arm pivotally mounted on the switch member, means biasing said actuating to an operative position, a roller on said actuating arm engageable with th switch arm to move said switch arm to an open position when the switch member is moved to closed position, means on said support member engageable by the roller to move the actuating arm to restraining position, and means on the switch member for cooperating with the roller to restrain the switch arm in open position when the circuit breaker is in closed position.

10. A circuit breaker comprising a switch member movable to open and closed positions, operating mechanism for moving said switch member to open and to closed position, a field discharge switch comprising a stationary contact and a cooperating switch arm, an actuating member for said field discharge switch pivotally mounted on a part movable with the switch member, means on said part for cooperating with the actuating member to releasably restrain the switch arm in open position when the switch member is in closed position, means biasing the switch arm in a closing direction and operable during opening movement of the switch member to close the field discharge switch, said actuating member being biased to an operative position and operable during closing movement of the switch member to actuate the switch arm to open position.

11. A circuit breaker comprising a switch member movable to an open and to a closed position, operatin mechanism for moving said switch member to open and to closed position, a field discharge switch comprising a stationary contact and a switch arm biased in a closing direction and movable to an open position, an actuating arm mounted on a part movable with the switch member, said actuating arm being engageable with the switch arm to actuate said switch arm to open position when the switch member is moved to closed position, said actuating arm being movable to a restraining position, and restraining means on a part movable with the switch member for cooperating with the actuating arm to releasably restrain the switch arm in open position, said restraining means being adjustable to vary the time at which the field discharge switch will clos during an opening movement of the switch member.

12. A circuit breaker comprising a switch member, operating mechanism for moving said switch member to an open and to a closed position, a, field discharge switch mounted in detached relation with the circuit breaker mechanism and comprising a stationary contact and a movable contact member, actuating means for said contact member comprising an arm pivotally mounted on the switch member, said actuating means being operable to move the contact member to open position when the switch member is moved to closed position, means engageable with said actuating means to move said actuating means to a restraining position, and a stop member on the switch member for cooperating with the actuating means to restrain the contact member in open position when the switch member is in closed position, said stop member being adjustable to adjustably determine the open air gap of the field discharge switch.

13. A circuit breaker comprising a switch member movable to an open and to a closed position, operating mechanism for moving said switch member to open and to closed position, a field discharge switch comprising a, stationary contact and a pivoted switch arm, a cam member on said switch arm, an actuating arm pivotally mounted on the switch member and engageable with said cam member to move the pivoted switch arm to open position when the switch member is moved to closed position, said cam member acting to move the actuating arm to a restraining position near the end of the closing movement of the switch member, and adjustable means on the switch member 'ior cooperating with the actuating arm when said arm is in restraining position to restrain the switch arm in open position, and resilient means for moving said switch arm to closed position when the switch member is moved'to open position.

14. A circuit breaker comprising a switch member movable to an open and to a closed posi-' tion, operating mechanism for said switch member, a field discharge switch comprising a stationary contact and a movable switch arm, support means for pivotally supporting said switch arm, an actuating arm mounted on the switch member and engageable with said switch arm to move said switch arm to open position when the switch member moves to closed position, a cam member on said support means engageable by the actuating arm to move said actuating arm to a restraining position near the end of the movement of the switch member to closed position, a stop member on the switch member for cooperating with the actuating member to restrain the switch arm in open position, and means comprising a spring for moving said switch arm to closed position when the switch member is moved to open position.

15. A circuit breaker comprising relatively movable contacts, a switch member movable to an open and a closed position to open and close said contacts, operating mechanism for moving said switch member to open and to closed position, a field discharge switch including a sta tionary contact, a switch arm mounted on a fixed pivot, means biasing said switch arm to closed position, and actuating means for the switch arm movable with the switch member, said actuating means being operable during closing of the breaker to engage and efiect opening of the field discharge switch prior to closing of the contacts of the breaker and said actuating means being separable from the switch arm during opening of the breaker to cause closing of said field discharge switch prior to opening of the breaker contacts.

TURE LINDSTROM. 

